Drive controller, imaging apparatus and drive control method

ABSTRACT

There is provided a drive controller including a determination part that compares a target stop position of a movable body, which is driven by a piezoelectric actuator driven by a piezoelectric element expanded and contracted in response to an applied voltage, with a real position of the movable body acquired on the basis of a position sensor, and determines whether or not the target stop position matches with the real position, and a drive control part that turns off energization of the piezoelectric actuator when the target stop position matches with the real position while the movable body is being driven by the piezoelectric actuator.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 14/499,661, filed Sep. 29, 2014, which claimspriority from prior Japanese Priority Patent Application JP 2013-214726filed in the Japan Patent Office on Oct. 15, 2013, the entire contentsof which are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a drive controller that controls astop of a movable body driven by a drive part, an imaging apparatus anda drive control method.

For an autofocus function, an electrically-driven zoom function and acamera shake correction mechanism, an electromagnetic conversion motorusing a coil and a magnet such as a stepping motor, a voice coil motorand a DC motor is often used. In the electromagnetic conversion motor,it is difficult to keep the position when energization of the motor isturned off. In particular, when the energization is suddenly turned OFFin the middle of high-speed drive, the motor is affected by inertia of alens movable part and is stopped at a position past the position atwhich the energization is turned off. Therefore, generally from aviewpoint of saving power or the like, when turning off theenergization, it may be necessary to turn off the energization onlyafter the movable body is completely stopped after a stop is instructed.

In a stepping motor for instance, as disclosed in JP2006-158019A, afterthe end of microstep drive, a rotor is driven to make an excitationposition of the rotor coincide with an excitation position of a stator,and then energization of the motor is turned off. This prevents themotor from stopping out of an originally intended position at which themotor should actually be stopped due to detent torque that the motorhas.

SUMMARY

However, in the case of tentatively stopping a motor, then moving themotor further to a stably stopped position, and turning off theenergization of the motor thereafter as described in JP2006-158019A, ittakes a very long time from drive to turning off of the energization.For instance, when using such a method in an autofocus (AF) mechanism,autofocusing time (that is, a shutter time lag) becomes extremely long.Not to mention, when the energization of the motor is suddenly turnedoff during high-speed drive, inertia causes a state called step-out inwhich synchronization of an energization signal and a motor rotationangle is shifted, and the motor not only passes by a stop position butalso loses the motor rotation angle (that is, a focus position). Also,when the motor is disturbed by an impact or the like while theenergization of the motor is off, the position is shifted to a stablystopped position different from an original stop position or slightshift from the original stop position is generated even within thestably stopped position close to the desired stop position.

Similarly in a DC motor, even when the energization is turned off afterthe motor is stopped, the misalignment occurs due to the influence ofthe detent torque, and when the energization of the motor is turned offduring the high-speed drive, the motor is stopped at a position past theoriginal stop position due to the influence of the inertia. Theovershoot is not stable due to the influence of variation of loads ofthe motor and a gear mechanism, and it is extremely difficult to predictthe overshoot and perform correction beforehand for turning off theenergization of the motor before the original stop position.

In a voice coil motor, in its principle of controlling a position of amovable body using feedback control using information from a positionsensor, the position of the movable body is completely unfixed when theenergization of the motor is turned off to begin with. Also, even in thestate of stopping by controlling the stop by servo drive, the movablebody is not completely stopped due to the influence of signal noise ofthe position sensor that detects a real position of the movable body orthe like, and maintains the positions while finely moving. Therefore,compared to the case that the energization is turned off, the motor isdegraded in stop accuracy.

In such a manner, it is difficult to quickly stop the motor during thehigh-speed drive in a short time while maintaining high stop accuracy,and not to mention, turning off the energization of the motor duringdrive causes a large misalignment of the movable body. Further, themotor is easily influenced by disturbance such as signal noise, animpact or the like, the misalignment easily occurs, and positionaccuracy when the movable body is stopped is affected.

Accordingly, the present disclosure proposes a new and improved drivecontroller, imaging apparatus and drive control method capable ofstopping a drive part that drives the movable body quickly with highaccuracy and achieving power consumption reduction by turning off theenergization of the drive part.

According to an embodiment of the present disclosure, there is provideda drive controller including a determination part that compares a targetstop position of a movable body, which is driven by a piezoelectricactuator driven by a piezoelectric element expanded and contracted inresponse to an applied voltage, with a real position of the movable bodyacquired on the basis of a position sensor, and determines whether ornot the target stop position matches with the real position while themovable body is being driven by the piezoelectric actuator, and a drivecontrol part that turns off energization of the piezoelectric actuatorwhen the target stop position matches with the real position.

According to another embodiment of the present disclosure, there isprovided an imaging apparatus including an imaging unit, a lens partcomposed of one or more lenses that transmit light incident on theimaging unit, a plurality of drive parts that move a movable body thatholds the imaging unit and the lenses respectively and moves in apredetermined direction respectively, and a plurality of drive controlparts that control the individual drive parts respectively. At least oneof the drive parts is a piezoelectric actuator that drives the movablebody with a piezoelectric element expanded and contracted in response toan applied voltage. The drive control part of the piezoelectric actuatorincludes a determination part that compares a target stop position ofthe movable body with a real position of the movable body acquired onthe basis of a position sensor, and determines whether or not the targetstop position matches with the real position while the movable body isbeing driven by the piezoelectric actuator, and a drive control partthat turns off energization of the piezoelectric actuator when thetarget stop position matches with the real position.

According to another embodiment of the present disclosure, there isprovided a drive control method including comparing a target stopposition of a movable body, which is driven by a piezoelectric actuatordriven by a piezoelectric element expanded and contracted in response toan applied voltage, with a real position of the movable body acquired onthe basis of a position sensor, and determining whether or not thetarget stop position matches with the real position while the movablebody is being driven by the piezoelectric actuator, and turning offenergization of the piezoelectric actuator when the target stop positionmatches with the real position.

According to the present disclosure, when moving the movable body movedby a piezoelectric actuator to a target stop position, the drivecontroller compares the target stop position of the movable body with areal position, and when determining that they match during the drive ofthe movable body by the piezoelectric actuator, turns off theenergization to the piezoelectric actuator. Thus, the time required formoving the movable body to the target stop position can be shortened andthe movable body can be stopped at the target stop position with highaccuracy. By turning off the energization of the piezoelectric actuator,the power consumption reduction can be also achieved.

As described above, according to the present disclosure, the drive partthat drives the movable body can be stopped quickly with high accuracy,and the power consumption reduction by turning off the energization ofthe drive part can be achieved. Also, the above-described effects arenot necessarily definite, and together with the above-described effects,or instead of the above-described effects, one of effects indicated inthis specification or other effects that can be recognized from thisspecification may be demonstrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating a front surface sideappearance of an imaging apparatus according to a first embodiment ofthe present disclosure;

FIG. 2 is a perspective view illustrating a lens drive mechanism of afocus lens which is one of drive parts of the imaging apparatusaccording to the embodiment;

FIG. 3 is a perspective view illustrating a lens frame which is amovable body driven by the lens drive mechanism according to theembodiment;

FIG. 4 is a planar sectional view of the lens drive mechanism of theimaging apparatus according to the embodiment;

FIG. 5 is an explanatory diagram illustrating a deceleration operationof the focus lens generated during servo control;

FIG. 6 is an explanatory diagram illustrating an overshoot operation ofthe focus lens generated during the servo control;

FIG. 7 is an explanatory diagram illustrating stop control of the focuslens according to the embodiment;

FIG. 8 is a block diagram illustrating one configuration example of adrive controller according to the embodiment;

FIG. 9 is a flowchart illustrating processing of drive stop control ofthe focus lens by the drive controller according to the embodiment;

FIG. 10 is an explanatory diagram illustrating drive control by thedrive controller according to a second embodiment of the presentdisclosure;

FIG. 11 is a control block diagram of the drive controller according toa third embodiment of the present disclosure; and

FIG. 12 is an explanatory diagram illustrating correction of a targetstop position by the drive controller according to the embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the appended drawings, structural elementsthat have substantially the same function and structure are denoted withthe same reference numerals, and repeated explanation of thesestructural elements is omitted.

Descriptions will be given in the following order.1. First embodiment (drive stop control by comparison between targetstop position and real position of movable body)

1.1. Configuration of imaging apparatus

1.1.1. Entire configuration of imaging apparatus

1.1.2. Configuration of drive part

1.1.3. Movement of lens frame by piezoelectric actuator

1.2. Drive control of drive part

1.2.1. Outline of drive control by drive controller

1.2.2. Configuration of drive controller

1.2.3. Focus lens drive stop control by drive controller

1.3. Summary

2. Second embodiment (timing of turning off energization ofpiezoelectric actuator)3. Third embodiment (correction of target stop position)

1. First Embodiment [1.1 Configuration of Imaging Apparatus]

First, with reference to FIG. 1-FIG. 4, one configuration example of animaging apparatus according to a first embodiment of the presentdisclosure will be described. FIG. 1 is a schematic perspective viewillustrating a front surface side appearance of the imaging apparatusaccording to the present embodiment. FIG. 2 is a perspective viewillustrating a lens drive mechanism of a focus lens 121 which is one ofdrive parts of the imaging apparatus according to the presentembodiment. FIG. 3 is a perspective view illustrating a lens frame 300which is a movable body driven by the lens drive mechanism according tothe present embodiment. FIG. 4 is a planar sectional view of the lensdrive mechanism of the imaging apparatus according to the presentembodiment.

(1.1.1. Entire Configuration of Imaging Apparatus)

In the present embodiment, the case of application to the drive controlof the focus lens 121 of a digital still camera 100 illustrated in FIG.1 will be described. The digital still camera 100 includes a body part110 having a control part that controls the entire imaging apparatus, animaging device, a signal processing part that processes image signalsacquired by the imaging device and the like, and a lens part 120 havinga zoom lens, a focus lens, a correction lens part and the like.

The body part 110 has the control part that controls the entire imagingapparatus, the imaging device, the signal processing part that processesimage signals that are electric signals corresponding to image dataacquired by the imaging device and the like. As the imaging device, forinstance, the imaging device such as a charge coupled device (CCD) typeimage sensor, a complementary metal oxide semiconductor (CMOS) typeimage sensor and the like is usable. In the case of using the CMOS typeimage sensor as the imaging device, the imaging device converts anoptical image formed on an imaging surface to an electric signal.

The electric signal which is an image signal is subjected to noiseelimination processing and gain control processing of turning an imagingsignal to a desired signal level, then converted from an analog signalto a digital signal, and outputted to the signal processing part. Thesignal processing part carries out, to the inputted electric signal,defect correction processing of correcting a signal of a defective pixelin the imaging device, shading correction processing of correcting areduction in peripheral light quantity of the lens, and processing ofwhite balance adjustment, luminance correction and the like. Theelectric signal processed by the signal processing part is outputted toan output part such as a display for instance as image data.

The lens part 120 includes the zoom lens that varies magnification, thefocus lens that carries out focusing, the correction lens part thatmoves a position of the optical image formed on the imaging surface ofthe imaging device on the imaging surface and the like. The zoom lens,the focus lens and the correction lens part may be driven on the basisof lens control signals from the control part, or may be driven byuser's operation. Also, the lens part 120 includes a mechanical shutterthat mechanically adjusts an exposure amount to the imaging surface ofthe imaging device, and a diaphragm mechanism that adjusts a lightquantity of the optical image formed on the imaging surface of theimaging device.

Lens positions of the zoom lens and the focus lens, a displacement stateof the correction lens part, a setting position of the diaphragmmechanism and the like are detected by an optical system sensor, andoutputted to the control part as position signals. Also, the lens partis provided with a driver that drives the zoom lens, the focus lens, thecorrection lens part, the diaphragm mechanism and the like on the basisof control signals from the control part.

(1.1.2. Configuration of Drive Part)

Such a digital still camera 100 has a drive part that moves the lens andthe imaging device to a predetermined position, and the drive part isused for focusing of the lens and for shake correction of the imagingdevice. As one configuration example of the drive part, the drive partthat drives the focus lens 121 will be described on the basis of FIG.2-FIG. 4.

The drive part that drives the focus lens 121 includes, as illustratedin FIG. 2, a fixing member 200 fixed to the digital still camera 100,and the lens frame 300 that supports the focus lens 121 and is providedon the fixing member 200 movably in an optical axis direction. The focuslens 121 and the lens frame 300 are also called the movable body.

The fixing member 200 is a roughly cylindrical member and includesannular surfaces 200 a, 200 b projected toward a center axis at bothends of an opening. At a hollow part of the fixing member 200, the lensframe 300 is arranged. The fixing member 200 includes a drive shaft 212and a sub shaft 240 of a piezoelectric actuator 210 provided in parallelwith an optical axis respectively at positions roughly facing each otherin a radial direction. By the drive shaft 212 and the sub shaft 240, thelens frame 300 is supported movably in an optical axis direction. Theoptical axis direction is identical to a center axis direction of thefixing member 200.

The piezoelectric actuator 210 includes a piezoelectric element 214expanded and contracted in response to an applied voltage, the driveshaft 212 connected to one end side in an expanding/contractingdirection of the piezoelectric element 214, and a weight 216 connectedto the other end side in the expanding/contracting direction of thepiezoelectric element 214. The piezoelectric element 214 and the driveshaft 212, and the piezoelectric element 214 and the weight 216 arefixed with an adhesive agent for instance.

The drive shaft 212 is a narrow round shaft member for instance. Thedrive shaft 212 is inserted to drive shaft support holes 201, 203respectively formed on the annular surfaces 200 a, 200 b of the fixingmember 200, and is slidably supported. Also, as illustrated in FIG. 4,with the drive shaft 212, a sliding contact surface 302 of the lensframe 300 is in contact between the drive shaft support holes 201, 203.

A drive shaft 212 is urged toward a sliding contact surface 302 by anurging member 230 fixed to the lens frame 300 with a fixing member 232such as a screw, and is frictionally connected with the lens frame 300.Since the drive shaft 212 and the sliding contact surface 302 of thelens frame 300 are frictionally connected, the lens frame 300 can bemoved together with the drive shaft 212 moved in response to apiezoelectric element 214. For the urging member 230, a leaf spring orthe like for instance is usable. The urging member 230 is arranged sothat a direction of urging force that urges the drive shaft 212 turns tothe direction where a sub shaft 240 is arranged. By the urging member230, it is possible to suppress inclination of the lens frame 300 andmovement of the lens frame 300 in directions other than a drivingdirection.

By frictional force generated between the drive shaft 212 and thesliding contact surface 302 by the urging force of the urging member230, even in the state that the energization of the piezoelectricactuator 210 is turned off, positions of the drive shaft 212 and thesliding contact surface 302 can be held so as not to be shifted. Thus,the drive shaft 212 can be provided without play. The frictional forceis set at a value sufficiently large for weight of the movable bodycomposed of the focus lens 121 and the lens frame 300. That is, thefrictional force is set at such a value that the drive shaft 212 and thelens frame 300 can be held without a misalignment even against impactforce when the camera is hit and inertia generated when the movable bodyis suddenly stopped during drive. In this way, the drive shaft 212functions as a vibration member that drives the movable body, and alsofunctions as a support member that supports the lens frame 300 in anaxial direction.

The piezoelectric element 214 is expanded and contracted by a drivingpulse voltage applied between electrodes, and generates reciprocatingvibrations at different speeds. When the reciprocating vibrations of thepiezoelectric element 214 are transmitted to the drive shaft 212, thelens frame 300 frictionally connected to the drive shaft 212 is moved ina direction of the vibrations at a low speed by asymmetry of thereciprocating vibrations of the drive shaft 212.

A weight 216 is a member having predetermined weight, and thepiezoelectric actuator 210 is fixed to the fixing member 200 through theweight 216. The weight 216 is formed into a block shape for instance.

The sub shaft 240 is a narrow round shaft member for instance. The subshaft 240 is inserted and fixed to sub shaft support holes 202 and 204respectively formed on the annular surfaces 200 a, 200 b of the fixingmember 200. Also, the sub shaft 240 is inserted to a guide hole 332 ofthe lens frame 300 between the sub shaft support holes 202, 204. Thelens frame 300 is provided movably in the optical axis direction alongthe sub shaft 240.

In the present embodiment, the drive shaft 212 and the sub shaft 240 arearranged so as to hold a centroid of the movable body including the lens121 and the lens frame 300 therebetween. In this way, by arranging thecentroid of the movable body on a straight line connecting the driveshaft 212 and the sub shaft 240, force and moment applied to the movablebody can be supported with the minimum force by the drive shaft 212 andthe sub shaft 240. The drive device according to an embodiment of thepresent disclosure is not limited to the example, and the drive shaft212 and the sub shaft 240 may be arranged adjacently for instance.

Also, the fixing member 200 is provided with a magnetic sensor 224 as aposition sensor that detects a position of the lens frame 300 holdingthe focus lens 121. The magnetic sensor 224 is provided so as to face amagnet 222 provided on the lens frame 300 along the optical axisdirection. When the lens frame 300 is moved in the optical axisdirection in response to the vibrations of the piezoelectric actuator210, a position of the magnet 222 is also moved together with the lensframe 300. The magnetic sensor 224 specifies the position of the lensframe 300 by detecting intensity of a magnetic field that changesdepending on the position of the magnet 222.

The lens frame 300 is, as illustrated in FIGS. 2 to 4, a member that isarranged at the hollow part of the fixing member 200 and supports thefocus lens 121. The lens frame 300 includes a lens holding part 310 thatholds the focus lens 121, a first arm part 320 that is extended from thelens holding part 310 to the side of the drive shaft 212, and a secondarm part 330 extended from the lens holding part 310 to the side of thesub shaft 240.

On the first arm part 320, the sliding contact surface 302 that is incontact with the drive shaft 212 and supports it along the axialdirection is formed. At this time, the sliding contact surface 302 is,as illustrated in FIG. 4, arranged so as to be held between the driveshaft 212 and the sub shaft 240 in the view from a plane. The slidingcontact surface 302 is frictionally connected with the drive shaft 212urged toward a direction in which the sub shaft 240 is arranged by anurging member 230. Also, the sliding contact surface 302 is in contactwith an outer peripheral surface of the drive shaft 212 at a pluralityof parts, and is formed such that a cross sectional shape in a directionorthogonal to the optical axis is an almost V shape or an almost U shapefor instance.

In this way, by arranging the sliding contact surface 302 in a shape tobe in contact with an outer peripheral surface of the drive shaft 212 ata plurality of parts between the drive shaft 212 and the sub shaft 240,the lens frame 300 is prevented from being greatly moved in directionsother than a driving direction of the drive shaft 212 (that is, anoptical axis direction) due to an impact or the like. Note that, theposition of the lens frame 300 is normally regulated by the urgingmember 230 and projection parts 334, 334 to be described later. Also,generation of reaction against the urging force of the urging member 230can be reduced as well. A first arm part 320 is provided with a magnet222 so as to face a magnetic sensor 224 that detects the position of thelens frame 300.

On a second arm part 330, a guide hole 332 to which the sub shaft 240 isto be inserted is formed. The guide hole 332 is provided in order toprevent the lens frame 300 from being inclined due to the fall of thedigital still camera 100 or the like and giving an impact to thepiezoelectric element 214. Also, in the drive part according to thepresent disclosure, the guide hole 332 may not be provided all the time.An inner diameter of the guide hole 332 is larger than an outer diameterof the sub shaft 240, and the drive shaft 212 and the sub shaft 240originally arranged in parallel are formed so as to have such aclearance that the sub shaft 240 and the guide hole 332 are not broughtinto contact even when considering inclination of the sub shaft 240 thatis generated within dimensional tolerance of components.

Also, the second arm part 330 includes a pair of projection parts 334,334 in contact with an outer peripheral surface of the sub shaft 240 soas to hold the sub shaft 240 therebetween. For the projection parts 334,334, as illustrated in FIG. 5, the shape viewed from the front is formedinto a roughly semicircular block shape projected to the sub shaft 240for instance. Thus, the sub shaft 240 can be surely supported with fewcontact parts. Note that, the shape of the projection parts 334, 334 arenot limited to the example, and the shape viewed from the front may be aV shape projected to the sub shaft 240 for instance.

The projection parts 334, 334 are provided so as to hold the sub shaft240 therebetween from a rotating direction of the lens frame 300 withthe drive shaft 212 as the rotation center. Thus, the movement of thelens frame 300 rotating around the drive shaft 212 is regulated. Notethat, while the pair of projection parts 334, 334 are provided on a zaxis negative direction side with respect to the guide hole 332 asillustrated in FIG. 2 in the present embodiment, the present disclosureis not limited to the example, and the pair of projection parts 334, 334may be provided on a z axis positive direction side with respect to theguide hole 332. Also, the pair of projection parts 334, 334 may not bearranged closely in a z direction to the guide hole 332 as in thepresent embodiment, may be arranged at a predetermined distance in the zdirection from the guide hole 332 for instance, or may be providedinside the guide hole 332.

(1.1.3. Movement of Lens Frame by Piezoelectric Actuator]

The drive device according to the present embodiment moves the lensframe 300 that holds the focus lens 121 in the optical axis directionwith the piezoelectric actuator 210. The drive device is configured suchthat an optical axis C of the focus lens 121 held by the lens frame 300,the drive shaft 212 and the sub shaft 240 are parallel to one another.

When a voltage is applied to the piezoelectric element 214 of thepiezoelectric actuator 210, the piezoelectric element 214 is expanded,contracted and vibrated in a reciprocating manner. When reciprocatingvibrations of the piezoelectric element 214 are transmitted to the driveshaft 212, the lens frame 300 frictionally connected to the drive shaft212 is moved in a low-speed vibrating direction due to asymmetry of thereciprocating vibrations of the drive shaft 212. In this way, the lensframe 300 is moved in the optical axis direction in response to thevoltage applied to the piezoelectric element 214.

[1.2. Drive Control of Drive Part] (1.2.1. Outline of Drive Control byDrive Controller)

In the drive part of such a focus lens 121, the drive of thepiezoelectric actuator 210 that moves the focus lens 121 is controlledby the drive controller. In order to stop the focus lens 121 that ismoved at a correct focusing position, the drive controller according tothe present embodiment executes control so as to turn off a voltageapplied to the piezoelectric element 214 when the target stop positionof the focus lens 121 matches with a lens real position. Thus, the focuslens 121 can be stopped at the correct focusing position in a shorttime. In the present disclosure, the target stop position is a value setseparately from a drive instruction value which is a target controlposition of the focus lens 121 by servo control, and is a position wherethe focus lens 121 should actually be stopped.

For instance, in the case of receiving an arithmetic result of contrastAF or phase difference AF, moving the focus lens 121 to the focusingposition and stopping the focus lens 121, a conventional drivecontroller executes the servo control of making the focus lens 121follow so that the real position of the focus lens 121 matches with thedrive instruction value based on the arithmetic result. In the servocontrol, as illustrated in FIG. 5, in terms of characteristics of theservo control, the focus lens 121 is decelerated immediately before thetarget stop position of the focus lens 121, and it takes time to reachthe target stop position. Even though the focus lens 121 is notdecelerated depending on a servo parameter, an overshoot as illustratedin FIG. 6 is generated, and as a result, it takes time for convergenceuntil the focus lens 121 is stopped at the focusing position that is thetarget stop position.

After the movement of the drive part is converged and stopped, when theenergization of the drive part is turned off, autofocusing time becomeslong, and power consumption increases accordingly. In particular, in adevice such as a camera, there is a case that the energization of thedrive part of the focus lens 121 has to be turned off to supply power toa shutter due to a restriction of the maximum supply power. In such acase, the autofocusing time becomes extremely long.

Therefore, in the drive controller according to the present embodiment,as illustrated in FIG. 7, the energization of the piezoelectric actuator212 is turned off when the real position of the focus lens 121 detectedby the magnetic sensor 224 is in the target stop position at which thefocus lens 121 is actually desired to be stopped. Thus, a deceleratingaction before the stop position that is generated in terms ofcharacteristics of the servo as illustrated in FIG. 5 is eliminated, thefocus lens 121 can be brought close to the focus position while keepingthe highest moving speed, and the autofocusing time can be accelerated.

(1.2.2. Configuration of Drive Controller)

On the basis of FIG. 8, a configuration of a drive controller 430 of thepiezoelectric actuator 210 that drives the focus lens 121 according tothe present embodiment will be described. FIG. 8 is a block diagramillustrating one configuration example of the drive controller 430according to the present embodiment.

The drive controller 430 according to the present embodiment is a devicethat receives an arithmetic result of the contrast AF and the phasedifference AF by a camera control part 420, and controls thepiezoelectric actuator 210 such that the focus lens 121 is moved to thefocusing position which is the target stop position and stopped. Thedrive controller 430 includes, as illustrated in FIG. 8, a target stopposition acquisition part 432, a real position acquisition part 434, adetermination part 436, and a drive control part 438.

The target stop position acquisition part 432 acquires the focusingposition at which the focus lens 121 is actually desired to be stoppedas the target stop position from the camera control part 420. The cameracontrol part 420 carries out arithmetic processing of the contrast AFand the phase difference AF on the basis of operation input from anoperation input part 410 of the digital still camera 100 by a user, andcomputes the focusing position at which the focus lens 121 is actuallydesired to be stopped. When the target stop position of the focus lens121 is acquired from the camera control part 420, the target stopposition acquisition part 432 outputs the target stop position to thedetermination part 436 and the drive control part 438.

The real position acquisition part 434 computes and acquires an actualposition of the focus lens 121 driven by the piezoelectric actuator 210(also called “the real position of the focus lens 121”) on the basis ofa detection result by the magnetic sensor 224. The real positionacquisition part 434 outputs the acquired real position of the focuslens to the determination part 436 and the drive control part 438.

The determination part 436 compares the target stop position and thereal position of the focus lens 121, and determines whether or not thetarget stop position matches with the real position. A determinationmethod by the determination part 436 will be described later. Thedetermination part 436 outputs a determination result to the drivecontrol part 438.

The drive control part 438 controls the drive of the piezoelectricactuator 210 by controlling a voltage to be applied to the piezoelectricactuator 210 on the basis of the target stop position and the realposition of the focus lens 121. The drive control part 438 computes thedrive instruction value on the basis of the target stop position and thereal position of the focus lens 121, and drives the piezoelectricactuator 210 on the basis of the drive instruction value. The positionof the focus lens 121 moved by the drive of the piezoelectric actuator210 is cyclically detected by the magnetic sensor 224, and is outputtedto the real position acquisition part 434 each time. The processing isrepeatedly executed until it is determined by the determination part 436that the target stop position matches with the real position. Then, whenit is determined by the determination part 436 that the target stopposition matches with the real position, the drive control part 438turns off the energization of the piezoelectric actuator 210.

(1.2.3. Focus Lens Drive Stop Control by Drive Controller)

FIG. 9 illustrates processing of drive stop control of the focus lens121 by the drive controller 430 according to the present embodiment.

The drive stop control of the focus lens 121 according to the presentembodiment is started by receiving the operation input that may requireposition adjustment of the focus lens 121 for instance from theoperation input part 410 of the digital still camera 100 by the userfirst, as illustrated in FIG. 9 (S100). The operation input part 410outputs inputted operation input information to the camera control part420.

The camera control part 420 which receives the operation inputinformation carries out the arithmetic processing of the contrast AF andthe phase difference AF, and computes the focusing position at which thefocus lens 121 is actually desired to be stopped as the target stopposition (S102). The camera control part 420 outputs the computed targetstop position to the target stop position acquisition part 432 of thedrive controller 430. When the target stop position of the focus lens121 is acquired from the camera control part 420, the target stopposition acquisition part 432 outputs the target stop position to thedetermination part 436 and the drive control part 438.

In the meantime, the drive controller 430 acquires a detection value ofthe magnetic sensor 224 by the real position acquisition part 432, andcomputes and acquires the real position of the focus lens 121 (S104).The real position acquisition part 434 outputs the acquired realposition of the focus lens to the determination part 436 and the drivecontrol part 438.

Then, the drive controller 430 compares the target stop position of thefocus lens 121 acquired in step S102 and the real position of the focuslens 121 acquired in step S104 by the determination part 436 (S106).Then, the determination part 436 determines whether or not the targetstop position and the real position of the focus lens 121 match witheach other. The determination part 436 may, for instance, simply comparebetween the target stop position and the real position of the focus lens121 that are acquired, and determine whether or not these values matchwith each other.

Alternatively, the determination part 436 may take a difference betweenthe target stop position and the real position of the focus lens 121,and determine whether or not the target stop position matches with thereal position on the basis of whether or not a sign of the differencevalue is inverted. Due to influence of detection timing of the magneticsensor 224 or signal noise of the magnetic sensor 224 or the like, it ispossible that the focus lens 121 passes by the focusing position withoutthe target stop position and the real position completely matching witheach other. Therefore, by computing a difference between the target stopposition and the real position in real time during the drive of thefocus lens 121 and determining a moment at which the sign of thedifference value is inverted as the time when the target stop positionmatches with the real position, it is ensured that the focus lens 121can be stopped at the focusing position.

For instance, in an example illustrated in FIG. 7, the determinationpart 436 computes the difference value by subtracting the real positionfrom the target stop position of the focus lens 121. Thus, thedifference value is a positive value until the real position of thefocus lens 121 is in the target stop position. Then, when the realposition of the focus lens 121 exceeds the target stop position, thedifference value becomes a negative value. The determination part 436determines that the target stop position matches with the real positionat the timing at which the sign of the difference value between thetarget stop position and the real position of the focus lens 121 isinverted from being positive to negative.

Since the example in FIG. 7 illustrates the case that a focus positionmoves from a small value to a big value (that is, from bottom towardtop), the determination part 436 determines the timing at which the signof the difference value is inverted from being positive to negative. Forinstance, in the case that the focus position moves from a big value toa small value (that is, from top toward bottom), the difference valuefor which the real position is subtracted from the target stop positionbecomes the negative value until the real position of the focus lens 121is in the target stop position. Then, when the real position of thefocus lens 121 exceeds the target stop position, the difference valuebecomes the positive value. In this case, the determination part 436determines the timing at which the sign of the difference value isinverted from being negative to positive.

Also, as another determination method, the case that the differencevalue between the target stop position and the real position of thefocus lens 121 becomes equal to or smaller than a predeterminedthreshold value (coring) may be determined as the time when the targetstop position matches with the real position. In this case, since it isdifficult to achieve stop accuracy when exceeding the threshold (coring)of the focus lens 121, it is better to use the determination method bythe above-described sign inversion system when high accuracy isdemanded. A determination result in step S106 is outputted to the drivecontrol part 438.

Thereafter, the drive control part 438 controls the voltage to beapplied to the piezoelectric actuator 210 on the basis of thedetermination result in step S106. When it is determined that the targetstop position and the real position of the focus lens 121 do not matchwith each other in step S106, the drive control part 438 computes thedrive instruction value on the basis of the target stop position and thereal position, and drives the piezoelectric actuator 210 on the basis ofthe drive instruction value (S108). Then, the processing from step S104is repeatedly executed.

On the other hand, when it is determined that the target stop positionand the real position of the focus lens 121 match with each other instep S106, the drive control part 438 turns off the energization of thepiezoelectric actuator 210 (S110). Thus, the drive of the piezoelectricactuator 210 is stopped. At this time, since the drive shaft 212 of thepiezoelectric actuator 210 is urged to the sliding contact surface 302of the lens frame 300 by the urging member 230, the lens frame 300 cankeep the position when the energization of the piezoelectric actuator210 is turned off.

[1.3. Summary]

The configuration of the drive controller 430 of the drive partaccording to the first embodiment of the present disclosure and theoperation thereof are described above. According to the presentembodiment, in order to stop the focus lens 121 that is moved at thecorrect focusing position, the drive controller 430 executes control soas to turn off the voltage applied to the piezoelectric element 214 whenthe target stop position and the real position of the focus lens 121match with each other. Thus, the focus lens 121 can be stopped at thecorrect focusing position in a short time. Also, by quickly moving andstopping the focus lens 121, the time during which the energization ofthe piezoelectric actuator 210 is turned off can be prolonged, and powerconsumption can be reduced.

2. Second Embodiment

Next, on the basis of FIG. 10, the drive control method by the drivecontroller according to the second embodiment of the present disclosurewill be described. FIG. 10 is an explanatory diagram illustrating drivecontrol by the drive controller according to the present embodiment. Theconfiguration of the drive controller according to the presentembodiment and the imaging apparatus including the drive controller isthe same as the configuration in the first embodiment illustrated inFIG. 1-FIG. 4 and FIG. 8, so that it is described using the samereference numerals and detailed descriptions are omitted.

In the case of adopting drive utilizing a PWM waveform as a drive methodof the piezoelectric actuator 210, a drive voltage applied to thepiezoelectric actuator 210 is indicated by a cyclic rectangular wave asin each graph indicated on a lower side of FIG. 10 for instance. Here,when the energization of the piezoelectric actuator 210 is turned off inthe middle of one cycle of the rectangular wave, as in the graphindicated at the lower left of FIG. 10, a shape of the rectangular wavebecomes a halfway shape. Such output affects an expansion andcontraction operation of the piezoelectric actuator 210 and sound isgenerated when the energization is turned off.

Accordingly, in the drive controller 430 according to the presentembodiment, as illustrated at the lower right of FIG. 10, theenergization of the piezoelectric actuator 210 is turned off after therectangular wave of the drive voltage is outputted for one cycle afterthe sign of the difference value between the target stop position andthe real position of the focus lens 121 is inverted. That is, after itis determined that the target stop position and the real position of thefocus lens 121 match with each other, at the point of time at which thevalue of the PWM waveform of the drive voltage cyclically applied to thepiezoelectric actuator 210 becomes zero, the energization of thepiezoelectric actuator 210 is turned off.

In this way, when it is determined that the target stop position and thereal position of the focus lens 121 match with each other, the drivecontroller 430 according to the present embodiment does not turn off theenergization of the piezoelectric actuator 210 immediately in the middleof output of the rectangular wave of the drive voltage for one cycle.The drive control part 438 of the drive controller 430 shifts theswitching timing of a driver, and turns off the energization of thepiezoelectric actuator 210 consistently at the timing at which theoutput of the waveform for one cycle is ended. Thus, influence on theexpansion and contraction operation of the piezoelectric actuator 210 isreduced, and the sound generated when the energization of thepiezoelectric actuator 210 is turned off is reduced.

In the drive control according to the present embodiment, there is acase that the time of turning off the energization of the piezoelectricactuator 210 is slightly delayed from the time when it is actuallydetermined that the target stop position and the real position of thefocus lens 121 match with each other. However, since the delay issufficiently short time to the speed of focus, position control of thefocus lens 121 is not greatly affected.

The timing of turning off the energization of the piezoelectric actuator210 by the drive controller 430 according to the present embodiment iseffective when the imaging apparatus is performing imaging in a movingimage mode in particular. By the drive control, the sound generated whenthe energization of the piezoelectric actuator 210 is turned off doesnot obstruct the sound acquired together with images during the movingimage mode.

3. Third Embodiment

On the basis of FIG. 11 and FIG. 12, the drive control method by thedrive controller according to the third embodiment of the presentdisclosure will be described. FIG. 11 is a control block diagram of thedrive controller according to the present embodiment. FIG. 12 is anexplanatory diagram illustrating correction of the target stop positionby the drive controller according to the present embodiment. Note that,in the present embodiment, the configuration of the drive controller andthe imaging apparatus including the drive controller is the same as theconfiguration in the first embodiment illustrated in FIG. 1-FIG. 4 andFIG. 8, so that it is described using the same reference numerals anddetailed descriptions are omitted.

A detection signal of the magnetic sensor 224 that is information on thereal position of the focus lens 121 generally includes signal noise. Inorder to eliminate the signal noise, in the drive controller 430, asillustrated in FIG. 11, a low-pass filter (also called “LPF”,hereinafter) is often applied to the detection signal of the magneticsensor 224.

In the case of utilizing real position information of the focus lens 121after applying the LPF, for determination of turning off of theenergization of the piezoelectric actuator 210 according to the firstembodiment, the real position of the focus lens 121 is delayed timewisefrom the original real position due to a delay element of the LPF. Thatis, while the real position of the focus lens 121 is a positionindicated by a thick dashed line in FIG. 12, when the delay element ofthe LPF is included in the real position of the focus lens 121, timedelay is generated as indicated by the dashed line. Therefore, whenturning off of the energization of the piezoelectric actuator 210 isdetermined utilizing the information delayed by the LPF, the focus lens121 is to be stopped past the target stop position by a distance x inFIG. 12.

In the meantime, a delay amount of the LPF is uniquely determined by adrive speed of the focus lens 121. Thus, it is possible to obtain thedelay amount by calculation from design information of the LPF for thedrive speed. Then, the drive controller 430 according to the presentembodiment brings forward the timing of turning off the energization ofthe piezoelectric actuator 210 depending on the moving speed of thefocus lens 121 when moving to the target stop position, and sets thetarget stop position by the delay amount before in the drivingdirection. Thus, the focus lens 121 can be accurately stopped at thefocusing position which is the original target stop position.

The delay mount of the LPF is changed by a setting value of the LPF aswell. Normally, the setting value of the LPF is not changed when it isonce set. Therefore, the delay element generated by the setting may betaken into consideration when designing the LPF, to correct the targetstop position.

Note that, as another method of avoiding overshooting of the focus lens121 due to the delay element of the LPF, the following method can beconsidered. For instance, an advance compensator is introduced after adigital LPF illustrated in FIG. 11 to advance for the delay. Further,preceding information of an analog LPF illustrated in FIG. 11 may beused for information to be used to determine turning off of theenergization of the piezoelectric actuator 210, and a value through theLPF illustrated in FIG. 11 may be used for position information of thefocus lens 121 to be used for the servo operation. Thus, only theovershoot can be improved without damaging a servo performance.

The preferred embodiments of the present disclosure are described abovein detail with reference to the appended drawings, but the technicalscope of the present disclosure is not limited to the examples. It isclear that a person ordinarily skilled in the art of the presentdisclosure can conceive various kinds of change examples or correctionexamples within the scope of technical ideas described in the claims,and it is understood that they of course belong to the technical scopeof the present disclosure.

For instance, while the lens drive method of the AF operation isdescribed in the above-described embodiment, the present technology isnot limited to the example. For instance, the present technology isapplicable to various drive modes regarding a lens movable part such asmanual focus and zoom operations or the like. By applying the drivecontrol according to the embodiment, it is possible to obtain theeffects similar to the present disclosure such as shortening ofoperation time, reduction of power consumption, and reduction ofenergization off sound.

Also, in the above-described embodiment, the drive controller that turnsoff the energization of the piezoelectric actuator 210 at the timing atwhich the target stop position and the real position of the focus lens121 match with each other in the drive stop of the piezoelectricactuator 210 is described. The imaging apparatus according to thepresent technology may further include, other than the drive controlleraccording to the above-described embodiment, a second drive controllerthat controls the piezoelectric actuator 210 so that the focus lens 121is stopped at the target stop position by feedback control based on adetection result of the position sensor.

At this time, the imaging apparatus controls the piezoelectric actuator210 by either one of the drive controller according to theabove-described embodiment and the second drive controller on the basisof a function state of the imaging apparatus. Since the drive controlleraccording to the above-described embodiment turns off the energizationof the piezoelectric actuator 210 instantaneously when the target stopposition and the real position of the movable body match with eachother, it is better to apply the drive controller when the movable bodymoves in a little amount. For instance, the piezoelectric actuator 210is controlled by the drive controller according to the above-describedembodiment in a still image photographing mode of photographing stillimages, and the piezoelectric actuator 210 is controlled by the seconddrive controller in a moving image photographing mode of photographingmoving images.

When photographing the moving images with the possibility that the focuslens 121 is frequently driven, the energization of the piezoelectricactuator 210 is turned off after the movement of the movable body isconverged. On the other hand, when photographing the still images, theenergization of the piezoelectric actuator 210 is turned off when thereal position of the movable body is in the target stop position, sothat the power consumption can be reduced.

Also, the effects described in this specification are only explanationsor examples and are not definite. That is, the technology according tothe present disclosure can demonstrate other effects that are clear tothose skilled in the art from descriptions of this specification,together with the above-described effects, or instead of theabove-described effects. Additionally, the present technology may alsobe configured as below.

(1) A drive controller including:

a determination part that compares a target stop position of a movablebody, which is driven by a piezoelectric actuator driven by apiezoelectric element expanded and contracted in response to an appliedvoltage, with a real position of the movable body acquired on the basisof a position sensor, and determines whether or not the target stopposition matches with the real position; and

-   -   a drive control part that turns off energization of the        piezoelectric actuator when the target stop position matches        with the real position while the movable body is being driven by        the piezoelectric actuator.

(2) The drive controller according to (1),

wherein the determination part repeatedly calculates a differencebetween the target stop position and the real position, and when a signof the difference is inverted, determines that the target stop positionmatches with the real position.

(3) The drive controller according to (1) or (2),

wherein the target stop position is a position where the movable body isactually stopped, which is set separately from a drive instruction valuewhich is a target control position of the movable body by servo control.

(4) The drive controller according to any one of (1) to (3),

wherein, when the target stop position matches with the real position,the drive control part turns off the energization of the piezoelectricactuator at a point of time at which a value of a waveform of a drivevoltage cyclically applied to the piezoelectric actuator becomes zeroafter a point of time of the match.

(5) The drive controller according to any one of (1) to (4),

wherein the determination part corrects the target stop position inresponse to a delay element of the position sensor that detects the realposition.

(6) The drive controller according to (5),

wherein a correction amount of the target stop position is calculated onthe basis of a moving speed of the movable body.

(7) The drive controller according to any one of (1) to (6), including

a second drive control part that controls the piezoelectric actuator sothat the movable body is stopped at the target stop position by feedbackcontrol based on a detection result of the position sensor,

wherein the piezoelectric actuator is controlled by either one of thedrive control part and the second drive control part, on the basis of afunction state of a device provided with the movable body.

(8) An imaging apparatus including:

an imaging unit;

a lens part composed of one or more lenses that transmit light incidenton the imaging unit;

a plurality of drive parts that move a movable body that holds theimaging unit and the lenses respectively and moves in a predetermineddirection respectively; and

a plurality of drive control parts that control the individual driveparts respectively,

wherein at least one of the drive parts is a piezoelectric actuator thatdrives the movable body with a piezoelectric element expanded andcontracted in response to an applied voltage, and

wherein the drive control part of the piezoelectric actuator includes

-   -   a determination part that compares a target stop position of the        movable body with a real position of the movable body acquired        on the basis of a position sensor, and determines whether or not        the target stop position matches with the real position, and    -   a drive control part that turns off energization of the        piezoelectric actuator when the target stop position matches        with the real position while the movable body is being driven by        the piezoelectric actuator.

(9) The imaging apparatus according to (8),

wherein the piezoelectric actuator is composed of the piezoelectricelement and a drive shaft to be driven by the piezoelectric element, and

wherein the imaging apparatus includes an urging member that urges thedrive shaft to the movable body with fixed urging force.

(10) A drive control method including:

comparing a target stop position of a movable body, which is driven by apiezoelectric actuator driven by a piezoelectric element expanded andcontracted in response to an applied voltage, with a real position ofthe movable body acquired on the basis of a position sensor, anddetermining whether or not the target stop position matches with thereal position; and

turning off energization of the piezoelectric actuator when the targetstop position matches with the real position while the movable body isbeing driven by the piezoelectric actuator.

What is claimed is:
 1. A lens unit apparatus, comprising: at least onelens including a focus lens; a fixing member; a movable body on thefixing member, wherein the movable body is configured to hold the focuslens, and wherein the movable body is movable in a direction parallel toan optical axis of the at least one lens; a position sensor configuredto determine a current position of the movable body with respect to thefixing member, and a focus lens actuator configured to move the movablebody in the direction parallel to the optical axis of the at least onelens; and a circuitry configured to control the focus lens actuator, andturn off energization of the focus lens actuator while the movable bodymoves based on a determination that the current position of the movablebody matches a target focus position of the movable body.
 2. The lensunit apparatus according to claim 1, wherein the circuitry is furtherconfigured to turn off the energization based on a value of a waveformof a drive voltage.
 3. The lens unit apparatus according to claim 2,wherein, the circuitry is further configured to turn off theenergization of the focus lens actuator at a first point of time atwhich the value of the waveform of the drive voltage cyclically appliedto the focus lens actuator becomes zero after a second point of time ofthe match, based on the match of the target focus position with thecurrent position.
 4. The lens unit apparatus according to claim 1,wherein the circuitry is further configured to: control the focus lensactuator, and correct the target focus position of the movable bodybased on a delay associated with the position sensor.
 5. The lens unitapparatus according to claim 1, wherein the position sensor is amagnetic position sensor, wherein the fixing member is configured tohold the magnetic position sensor, and wherein the movable body isfurther configured to hold a magnet.
 6. The lens unit apparatusaccording to claim 1, wherein the circuitry is further configured to:repeat calculation of a difference between the target focus position andthe current position, and determine that the target focus positionmatches with the current position based on a sign of the differencebetween the target focus position and the current position determined asinverted.
 7. The lens unit apparatus according to claim 1, wherein thetarget focus position is a position where the movable body is stopped,and is set separately from a drive instruction value which is a focuscontrol position of the movable body based on a servo control.
 8. Thelens unit apparatus according to claim 4, wherein a correction amount ofthe target focus position is calculated based on a moving speed of themovable body.
 9. The lens unit apparatus according to claim 1, whereinthe circuitry is further configured to: control the focus lens actuatorso that the movable body is stopped at the target focus position basedon a feedback control and a detection result of the position sensor, andcontrol the focus lens actuator based on a function state of a devicewith the movable body.
 10. The lens unit apparatus accordingly to claim1, wherein the focus lens actuator is a piezoelectric actuator that isconfigured with a piezoelectric element expanded and contracted based onan applied voltage.
 11. The lens unit apparatus accordingly to claim 10,wherein the applied voltage is a pulse width modulated (PWM) waveformwith periodic rectangular waves of voltage applied to the piezoelectricactuator.
 12. The lens unit apparatus accordingly to claim 11, whereinturning off the energization of the piezoelectric actuator includesturning off the PWM waveform of the voltage applied to the piezoelectricactuator at an end of a cycle associated with the periodic rectangularwaves.
 13. The lens unit apparatus accordingly to claim 1, wherein thetarget focus position is obtained from a camera control part based on atype of autofocus employed, wherein the type of autofocus is at leastone of a Contrast Autofocus or a Phase Difference Autofocus.
 14. Thelens unit apparatus accordingly to claim 1, further comprising: alow-pass filter (LPF) configured to filter a detection result of theposition sensor.
 15. The lens unit apparatus accordingly to claim 4,wherein the delay is changed by a setting value of a low pass filter(LPF).
 16. The lens unit apparatus accordingly to claim 4, wherein thecurrent position is delayed timewise from an original current positionbased on the delay.
 17. The lens unit apparatus accordingly to claim 4,wherein the delay is determined based on a drive speed of the focuslens.
 18. An imaging apparatus, comprising: an imaging unit; a lens partwhich comprises at least one lens including a focus lens; a fixingmember; a movable body on the fixing member, wherein the movable body isconfigured to hold the focus lens, and wherein the movable body ismovable in a direction parallel to an optical axis of the at least onelens, and a position sensor configured to determine a current positionof the movable body with respect to the fixing member, and a focus lensactuator configured to move the movable body in the direction parallelto the optical axis of the at least one lens; and a circuitry configuredto: control the focus lens actuator, and turn off energization of thefocus lens actuator while the movable body moves based on adetermination that the current position of the movable body matches witha target focus position of the movable body.
 19. The imaging apparatusaccording to claim 18, wherein the focus lens actuator comprises a focuslens element and a drive shaft, wherein the drive shaft is driven by thefocus lens element, and wherein the imaging apparatus includes an urgingmember that is configured to urge the drive shaft to the movable bodywith a fixed urging force.
 20. A drive control method for a lens unit,comprising: moving a movable body in a direction parallel to an opticalaxis of at least one lens, wherein the movable body is configured tohold the at least one lens of the lens unit including a focus lens;determining a current position of the movable body with respect to afixing member based on a position sensor, turning off energization of afocus lens actuator while the movable body moves based on adetermination that the current position of the movable body matches witha target focus position of the movable body.